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Re: testsuite failure - 193 parallel execution

From: Eric Blake
Subject: Re: testsuite failure - 193 parallel execution
Date: Tue, 20 Jul 2010 15:11:33 -0600
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On 07/20/2010 03:05 PM, Paul Eggert wrote:
> Staring at the code some more I see another race condition
> that could explain the problem.  Suppose the parent, just
> after the last fork, races ahead of the child and jumps
> ahead to the "read at_token" cleanup loop.  The parent then
> executes the last "read at_token" cleanup at a point
> where the second-to-the-last child has already output
> its token, but before the second-to-the-last-child has
> closed the fifo.  The "read at_token" will then return 0 (because
> it sees end-of-file), but the parent incorrectly thinks
> that it has seen a token and then closes down the fifo
> before the last child gets a chance to write its token.

Hmm, maybe we should do more validation in the parent - not just read
from the fifo, but validate that we actually read a token.  That way, we
can ignore EOF (on the grounds that it may be a temporary condition, and
that more children remain to be run) and only advance when the token we
read back is non-empty.

Eric Blake   address@hidden    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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